Stacked body and method of producing stacked body

ABSTRACT

A stacked body includes a base including a plurality of insulating base material layers, a coil including a winding-shaped conductive pattern located on at least one of the plurality of the insulating base material layers, and an electrically isolated dummy pattern extending along at least a portion of the coil outside of the coil on at least one of the plurality of the insulating base material layers in a plan view, wherein the stacked body includes a step at which a thickness of the stacked body is different in a stacking direction, and the dummy pattern is located between the coil and the step at a portion defining the step where the thickness of the stacked body is larger.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to a stacked body including a circuitlocated on a base including an insulating base material layer, and amethod of producing such a stacked body.

2. Description of the Related Art

Japanese Unexamined Patent Publication No. H62-77048 describes a voicecoil motor including a coil and a permanent magnet. In this publication,a planar helical coil is formed on each of a plurality of substrates,and these substrates are stacked to form a coil.

Meanwhile, a voice coil motor is an actuator that utilizes a change in amagnetic field caused by a change in a current flowing through a coil,and a magnetic field generated by a permanent magnet. Such a voice coilmotor is used for a camera shake correction, etc. If the voice coilmotor has poor responsiveness, performance of a device to which thisvoice coil motor is used also becomes poor. Therefore, an actuatorhaving excellent responsiveness has been demanded, and for suchactuator, increasing electromagnetic force with an electromagnet hasbeen demanded.

SUMMARY OF THE INVENTION

A stacked body according to a preferred embodiment of the presentinvention includes a base including a plurality of insulating basematerial layers; a coil including a winding-shaped conductive patternlocated on at least one of the plurality of the insulating base materiallayers; and an electrically isolated dummy pattern extending along atleast a portion of the coil outside of the coil on at least one of theplurality of the insulating base material layers in a plan view; whereinthe stacked body includes a step at which a thickness of the stackedbody is different in a stacking direction; and the dummy pattern islocated between the coil and the step at a portion defining the stepwhere the thickness of the stacked body is larger.

With this configuration, the dummy pattern increases the intensityaround the step portion, thus preventing a loss of the shape of thestacked body.

The above and other elements, features, steps, characteristics andadvantages of the present invention will become more apparent from thefollowing detailed description of the preferred embodiments withreference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded perspective view of an electromagnet according toa first preferred embodiment of the present invention.

FIG. 2 is a sectional view of the electromagnet in FIG. 1 taken along aline II-II.

FIG. 3 is a view illustrating a magnetic field generated from theelectromagnet.

FIG. 4 is a view illustrating a magnetic field generated from anelectromagnet having no dummy pattern.

FIG. 5 is a graph illustrating a relationship between a current andelectromagnetic force to a time.

FIG. 6 is a view for describing a positional relationship between a coilconductor and a dummy pattern.

FIG. 7 illustrates a plan view of a camera module provided with theelectromagnet according to a preferred embodiment of the presentinvention, and a sectional view taken along a line VII-VII.

FIGS. 8A and 8B are views illustrating an example in which a frame isdisplaced in an X direction.

FIG. 9 is a perspective view of an electromagnet different from theelectromagnet according to a first preferred embodiment of the presentinvention.

FIG. 10 is an exploded perspective view of an electromagnet according toa second preferred embodiment of the present invention.

FIG. 11 is a view illustrating one example of an in-plane coil conductorand a dummy pattern, each including a stress distribution portionprovided thereon.

FIG. 12 is a front sectional view of an electromagnet according to athird preferred embodiment of the present invention.

FIG. 13 is a perspective view of an electromagnet according to a fourthpreferred embodiment of the present invention.

FIG. 14 is an exploded view of an electromagnet according to the fourthpreferred embodiment of the present invention.

FIG. 15 illustrates a plan view of a camera module provided with theelectromagnet according to the fourth preferred embodiment of thepresent invention, and a sectional view taken along a line XV-XV.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First PreferredEmbodiment

FIG. 1 is an exploded perspective view of an electromagnet 1 accordingto a first preferred embodiment of the present invention, and FIG. 2 isa sectional view of the electromagnet 1 in FIG. 1 taken along a lineII-II.

The electromagnet 1 includes a stacked body 10 formed preferably byintegrally stacking insulating base material layers 11, 12, 13, and 14.Each of the base material layers 11 to 14 is made of thermoplastic resinhaving flexibility, such as LCP resin (liquid crystal polymer resin).The stacked body 10 is formed preferably by heat-sealing the basematerial layers 11 to 14 to one another by hot pressing.

A coil 20 is located on the stacked body 10. LCP resin has lowerdielectric constant than epoxy resin or ceramics. Therefore, the use ofLCP resin to the base material layers 11 to 14 decreases line-to-linecapacitance of the coil 20, and further, enables the formation of thecoil 20 at relatively low temperature. In addition, because of lowmagnetic permeability of the LCP resin, repulsive force generatedbetween windings of the coil 20 becomes low. Further, due to flexibilityof the LCP resin, the stacked body 10 is difficult to crack.

Examples of the thermoplastic resin include PEEK (polyether etherketone), PEI (polyether imide), PPS (polyphenylene sulfide), and PI(polyimide). These materials may be used instead of the liquid crystalpolymer resin. The stacked body 10 may include a base material layermade of low-melting-point thermosetting resin, or may not include a basematerial layer made of thermoplastic resin.

Although the stacked body 10 preferably includes a plurality of basematerial layers 11 to 14, it may include only one base material layer.The stacked body 10 is one example of a “base”.

Hereinafter, the planar direction of the base material layers 11 to 14is defined as X-Y direction, and the stacking direction of the basematerial layers 11 to 14 is defined as a Z direction. The coil 20 isprovided on the stacked body 10 with the Z direction being defined as acoil winding axis.

Terminal electrodes 11A and 11B are provided on one main surface (one ofa front surface and a back surface) of the base material layer 11. Theterminal electrodes 11A and 11B are input/output terminals of the coil20.

Each of in-plane coil conductors 12A, 13A, and 14A is provided on onemain surface (one of a front surface and a back surface) of each of thebase material layers 12 to 14. The in-plane coil conductors 12A, 13A,and 14A are one examples of a “winding-shaped conductive pattern”. Aninterlayer connection conductor indicated by a broken line in the figureis provided on each of the base material layers 12 to 14. The in-planecoil conductors 12A, 13A, and 14A are connected to one another with theinterlayer connection conductors, such that the coil 20 is arranged overa plurality of layers. More specifically, one ends of the in-plane coilconductors 12A and 13A are connected to each other. One ends of thein-plane coil conductors 13A and 14A are also connected to each other.

As described above, the coil 20 includes the in-plane coil conductors12A, 13A, and 14A, and the interlayer connection conductors. One end ofthe in-plane coil conductor 12A, which is a first end of the coil 20, isconnected to the terminal electrode 11A with the interlayer connectionconductor provided on the base material layer 11. One end of thein-plane coil conductor 14A, which is a second end of the coil 20, isconnected to the terminal electrode 11B with the interlayer connectionconductors provided on the base material layers 11 to 13. In this way,the coil 20 is disposed over a plurality of base material layers 11 to14 so as to extend while winding around toward the direction away fromthe base material layer 11, on which the terminal electrodes 11A and 11Bare provided, with the Z direction defined as the coil winding axis.

Dummy patterns 21, 22, and 23 are respectively provided on the basematerial layers 12 to 14. The dummy patterns 21 to 23 are provided onthe same main surfaces of the respective base material layers 12 to 14as the main surfaces on which the in-plane coil conductors 12A, 13A, and14A are located.

The dummy pattern 21 is preferably loop-shaped along an edge of the basematerial layer 12 such that the in-plane coil conductor 12A is locatedinside the loop. The dummy pattern 22 is preferably loop-shaped along anedge of the base material layer 13 such that the in-plane coil conductor13A is located inside the loop. The dummy pattern 23 is preferablyloop-shaped along an edge of the base material layer 14 such that thein-plane coil conductor 14A is located inside the loop.

The dummy patterns 21 to 23 are preferably located at a position wherethey overlap with each other in the Z direction. Interlayer connectionconductors 31, 32, 33, and 34 are provided on the base material layers12 and 13. The dummy patterns 21 and are connected to each other withthe interlayer connection conductors 31 and 32. The dummy patterns 22and 23 are connected to each other with the interlayer connectionconductors 33 and 34. These dummy patterns 21 to 23 and the interlayerconnection conductors 31 to 34 are electrically isolated from otherelements including the coil 20. As described later in detail, thesedummy patterns 21 to 23 and the interlayer connection conductors 31 todefine and function as a magnetic field shield for the magnetic fieldgenerated from the coil 20 upon the change in a current flowing throughthe coil 20, thus increasing the intensity of the magnetic field in theZ direction.

Each of the dummy patterns 21 to 23 may be provided on the other mainsurface opposite to the main surface on which each of the in-plane coilconductors 12A, 13A, and 14A is provided. The dummy patterns 21 to 23may not necessarily be provided on each of the base material layers 12to 14. For example, the dummy pattern may be provided on only thein-plane coil conductor 12A. It is only necessary that the dummypatterns 21 to 23 are located outside of the coil 20 in a plan view, andthey may be provided on a base material layer different from the basematerial layers 12 to 14 on which the in-plane coil conductors 12A, 13A,and 14A are located. For example, another base material layer may bestacked between the base material layers 11 and 12, and a dummy patternmay be provided on this base material layer.

The number and position of the interlayer connection conductorsconnecting the dummy patterns 21 to 23 are not particularly limited. Forexample, the interlayer connection conductor may be provided at only oneposition of the base material layer 12 for connecting the dummy patterns21 and 22. Alternatively, the interlayer connection conductors may beprovided at three or more positions of the base material layer 12 forconnecting the dummy patterns 21 and 22. In addition, the dummy patterns21 to 23 may not be connected with the interlayer connection conductor,but they may be independent of one another. Further, the interlayerconnection conductors 31 to 34 may be connected to only one of the dummypatterns 21 to 23. For example, the interlayer connection conductor 31may be connected to only the dummy pattern 21 without being connected tothe dummy pattern 22.

A non-limiting example of a production method of this electromagnet 1 isas described below.

Firstly, a copper foil is attached to one surface of a resin sheet.Alternatively, a sheet with copper attached to one surface is prepared.A resist film is patterned on the copper foil according to the terminalelectrodes 11A and 11B, the in-plane coil conductors 12A to 14A, and thedummy patterns 21 to 23 to be formed. An etching is performed to formeach pattern, and then, the resist film is removed. Thereafter, eachposition where the interlayer connection conductor is to be formed isirradiated with laser light from the other surface (on which the copperfoil is not attached) of each of the base material layers 11 to 13 toform a hole. A conductive paste containing Su, Cu, Ni, Ag, etc. isfilled in this hole. Thus, the base material layers 11 to 14 are formed.

The formed base material layers 11 to 14 are stacked. In this case, eachof the base material layers 11 to 14 is stacked on the main surface onwhich each pattern is formed. For example, the base material layer 13 isstacked on the base material layer 14 such that the contact surface withthe base material layer 14 becomes the main surface on which thein-plane coil conductor 13A is not formed. The base material layer 12 isstacked on the base material layer 13 such that the contact surface withthe base material layer 13 becomes the main surface on which thein-plane coil conductor 12A is not formed.

A heat and pressure treatment (hot press) is applied to the stacked basematerial layers 11 to 14 to bond these layers. The base material layers11 to 14 are thermoplastic as described above, so that an adhesive agentdoes not need to be used. Further, the insulating base material layer isa base material layer made of flexible resin, and this prevents damage(crack) upon curing. Thus, the electromagnet 1 is produced.

A permanent magnet 100 is provided just above the coil 20, such that theelectromagnet 1 thus configured is preferably used as a so-called voicecoil motor, for example. The portion just above the coil 20 is theposition which is opposite to the end of the stacked body 10 at the sideof the base material layer in the Z direction, and overlapped with theopening of the coil 20 in a plan view. The permanent magnet 100 includesan N pole and an S pole located along the X direction, and is capable ofreciprocating along the X direction.

When a current flows through the coil 20 in the electromagnet 1, amagnetic field occurs. The permanent magnet 100 disposed just above theelectromagnet 1 reciprocates along the X direction as indicated byarrows in the figure by electromagnetic force (magnetic attractive forceand magnetic repulsive force) caused by the magnetic field.Specifically, the reciprocating motion of the permanent magnet 100 ischanged according to the direction and power of electromagnetic force.

For example, in the case where a current flows through the coil 20 inthe direction from the terminal electrode 11A to the terminal electrode11B, the coil 20 includes an N pole at the side of the base materiallayer 11 and an S pole at the side of the base material layer 14. Inthis case, the S-pole end of the permanent magnet 100 is displaced withthe magnetic attractive force toward the portion just above the coil 20along the X-axis direction. When the value of the current flowingthrough the coil 20 is changed to increase (or decrease) the intensityof the magnetic field in this case, the magnetic attractive force isalso increased (or decreased) to raise (or reduce) the displacementspeed of the permanent magnet 100.

When the current flowing through the coil 20 is reversed, the polarityof the coil 20 is reversed, and the displacement direction of thepermanent magnet 100 is also reversed. More specifically, when thecurrent flows through the coil 20 in the direction from the terminalelectrode 11B to the terminal electrode 11A, the coil 20 includes an Spole at the side of the base material layer 11 and an N pole at the sideof the base material layer 14. In this case, the N-pole end of thepermanent magnet 100 is displaced toward the portion just above the coil20 along the X-axis direction with the magnetic attractive force.

In this way, the displacement speed and displacement direction of thepermanent magnet 100 in the X direction is changed by changing the leveland the direction of the current flowing through the coil 20.Accordingly, a voice coil motor with high responsiveness preferably isimplemented by enhancing a response of the permanent magnet 100 to thedisplacement speed and the displacement direction upon the change in thecurrent. The response of the permanent magnet 100 is enhanced byincreasing the electromagnetic force upon the change in the current.

In the present preferred embodiment, the electromagnet 1 includes thedummy patterns 21 to 23. The dummy patterns 21 to 23 are providedoutside of the coil 20. With this, the dummy patterns 21 to 23 preventthe spread of the magnetic field generated from the coil 20 in the Xdirection upon the change in the current. Accordingly, the magneticfield just above the coil 20 in the Z direction where the dummy patterns21 to 23 are not provided is able to be increased. Upon the change inthe current, the magnetic field just above the coil 20 is increased, sothat the electromagnetic force is also increased as described above.Accordingly, the response of the permanent magnet 100 is enhanced. Whenthe current value becomes constant, the magnetic flux generated from thecoil 20 passes through the dummy patterns 21 to 23. In other words, whenthe current value becomes constant, there is little difference in theintensity of the magnetic field due to the presence/absence of the dummypatterns 21 to 23.

The magnetic field generated from the electromagnet 1 will be describedbelow.

FIG. 3 is a view illustrating the magnetic field generated from theelectromagnet 1. FIG. 4 is a view illustrating a magnetic fieldgenerated from an electromagnet 1A having no dummy pattern. FIG. 4 is aview for comparison of FIG. 3. Similar to the electromagnet 1, theelectromagnet 1A illustrated in FIG. 4 has a coil 20 located on astacked body 10, but does not have a dummy pattern. Loop-shaped arrowsillustrated in FIGS. 3 and 4 indicate the magnetic field generated onthe coil 20 through which a current flows.

When a current flows through the coils 20 in the electromagnets 1 and 1Ain one direction, a loop-shaped magnetic field in the direction from theinside to the outside of the coil is generated. In the electromagnet 1including the dummy patterns 21 to 23 at the outside of the coil 20, thegenerated magnetic field passes between the coil 20 and the dummypatterns 21 to 23. In other words, the dummy patterns 21 to 23 defineand function as a magnetic field shield for preventing the spread of thegenerated magnetic field. On the other hand, in the electromagnet 1Ahaving no dummy patterns 21 to 23, the generated magnetic field spreadsin the X direction, compared to the electromagnet 1.

With this, upon the change in the current, the electromagnet 1 includingthe dummy patterns 21 to 23 has a higher magnetic flux density at aportion just above the coil 20 in the Z direction than the electromagnet1A having no dummy patterns, and therefore, the magnetic field isincreased. This increases the electromagnetic force just above the coil20.

FIG. 5 is a graph illustrating the relationship between a current andelectromagnetic force to a time.

In the upper graph in FIG. 5, a vertical axis indicates a current, and ahorizontal axis indicates a time. This graph illustrates that a valueand a direction of a current flowing through the coil 20 are changedwith time. In this graph, the flowing direction of the current isopposite between the case where the current value is plus and the casewhere the current value is minus. For example, the flowing direction ofthe current flowing through the coil 20 from times t0 to t3 and theflowing direction of the current flowing through the coil 20 from timest4 to t7 are opposite to each other. The current flowing through thecoil 20 increases from times t0 to t1 and times t6 to t7, the currentbecomes constant from times t1 to t2, times t3 to t4, and times t5 tot6, and the current decreases from times t2 to t3 and times t4 to t5.

In the lower graph in FIG. 5, a vertical axis indicates electromagneticforce, and a horizontal axis indicates a time. This graph illustratesthat electromagnetic force is changed according to a value and adirection of a current flowing through the coil 20. The direction inwhich the electromagnetic force is exerted in the X direction isopposite between the case where the current value is plus and the casewhere the current value is minus. For example, this graph illustratesthat the electromagnetic force is exerted in the opposite direction inthe X direction between the times t0 to t3 and the times t4 to t7.

In the lower graph in FIG. 5, the change in electromagnetic force in thecase where the dummy pattern is not provided is indicated by a brokenline, and the change in electromagnetic force in the case where thedummy patterns 21 to are provided is indicated by a solid line forcomparison. Comparing these two changes, the electromagnetic force inthe configuration having the dummy patterns 21 to 23 becomes sharplyhigher than the electromagnetic force in the configuration with no dummypatterns from the times t0 to t1, from the times t2 to t3, from thetimes t4 to t5, and from the times t6 to t7. In addition, theelectromagnetic force in the configuration with the dummy patterns 21 to23 is larger than the electromagnetic force in the configuration with nodummy patterns at times t1, t3, t5, and t7 at which the current ischanged.

Specifically, in the configuration including the dummy patterns 21 to23, the electromagnetic force exerted to the permanent magnet 100 uponthe change in the current is larger than that in the configurationwithout having the dummy patterns 21 to 23. Accordingly, theconfiguration including the dummy patterns 21 to 23 enhancesresponsiveness of the permanent magnet 100.

For example, from the times t0 to t3, the electromagnetic force becomessharply higher in the configuration having the dummy patterns 21 to 23than that in the configuration with no dummy patterns. With this, thepermanent magnet 100 is more rapidly displaced. At the time t3, theelectromagnetic force in the configuration having no dummy patterns iszero, while the electromagnetic force in the configuration having thedummy patterns 21 to 23 is exerted in the opposite direction of theelectromagnetic force generated from the times t0 to t3. Accordingly, inthe configuration having the dummy patterns 21 to 23, theelectromagnetic force in the direction opposite to the displacementdirection is exerted at the time t3 to the permanent magnet 100displaced in the X direction, such that the displacement of thepermanent magnet 100 is able to be instantaneously stopped.

As described above, the electromagnet 1 including the dummy patterns 21to 23 increases electromagnetic force upon the change in the current,thus enhancing responsiveness of the permanent magnet 100 upon thechange in the current. This configuration provides a voice coil motorhaving excellent responsiveness.

The preferable positional relationship between the coil 20 and the dummypatterns 21 to 23 to increase electromagnetic force of the electromagnet1 will be described below.

FIG. 6 is a view for describing a positional relationship between thecoil 20 and the dummy patterns 21 to 23. In this figure, the innerdiameter of the coil 20 is defined as X1, the distance between the coil20 and the dummy patterns 21 to 23 is defined as X2, and the patternwidth of each of the dummy patterns 21 to 23 is defined as X3.

The distance X2 between the coil 20 and the dummy patterns 21 to 23 ispreferably smaller, and X2 X1 is preferably satisfied. The width X3 ispreferably equal to or larger than a half of the inner diameter X1 (thedistance from the center of the opening of the coil to the inner edge).

The voice coil motor having the electromagnet 1 according to the presentpreferred embodiment is preferably used as a voice coil motor for acamera shake correction, for example. A camera module including thevoice coil motor for a camera shake correction will be described below.

FIG. 7 illustrates a plan view of a camera module 200 including theelectromagnet 1 according to the present preferred embodiment, and asectional view taken along a line VII-VII.

The camera module 200 includes a flexible substrate 101 and a frame 201.The frame 201 includes a lens holder 202 provided at the center of aflat plate, and this lens holder 202 holds a camera lens 203. Permanentmagnets 100A, 100B, 100C, and 100D are provided on the flat plate of theframe 201 so as to surround the lens holder 202 on all four sides.

The permanent magnets 100A and 100B are provided along the X directionacross the lens holder 202. Each of the permanent magnets 100A and 100Bincludes an N pole and an S pole along the X direction. The permanentmagnets 100C and 100D are provided along the Y direction across the lensholder 202. Each of the permanent magnets 100C and 100D includes an Npole and an S pole along the Y direction.

The frame 201 covers the permanent magnets 100A to 100D and the lensholder 202 and the like. However, FIG. 7 is a perspective view in whichthe permanent magnets 100A to 100D and the like covered by the frame 201are visible.

The flexible substrate 101 is provided below the frame 201 with a gap(e.g., 500 μm or less) between the frame 201 and the flexible substrate101. The frame 201 is displaceable in the X-Y plane. The flexiblesubstrate 101 and the frame 201 are connected with a wire 205, and thewire 205 defines and functions as a stopper of the frame 201 which isdisplaceable in the X-Y plane.

The flexible substrate 101 is formed preferably by stacking basematerial layers made of flexible thermoplastic resin. The flexiblesubstrate 101 has the configuration of the electromagnet 1 according tothe present preferred embodiment provided on regions A corresponding tothe permanent magnets 100A to 100D in the Z direction. When a currentflows through the coil conductors of the electromagnets 1 formed belowthe permanent magnets 100A and 100B, the frame 201 is displaced in the Xdirection. When a current flows through the coil conductors of theelectromagnets 1 below the permanent magnets 100C and 100D, the frame201 is displaced in the Y direction.

FIGS. 8A and 8B are views illustrating examples in which the frame 201is displaced in the X direction. For example, when a current flowsthrough the coil conductors of the electromagnets below the permanentmagnets 100A and 100B with the state illustrated in FIG. 8A, the frame201, and the lens holder 202 and the camera lens 203 provided to theframe 201 are displaced in the X direction (FIG. 8B). Although notillustrated, when a current flows through the coil conductors of theelectromagnets below the permanent magnets 100C and 100D, the frame 201,and the lens holder 202 and the camera lens 203 provided to the frame201 are displaced in the Y direction. With this, the camera lens 203 canbe displaced in the X-Y direction, such that a so-called camera shakecorrection is provided.

The electromagnet 1 according to the first preferred embodiment has beendescribed above. The number of the base material layers to be stackedcan appropriately be changed. Modifications of the electromagnet 1according to the first preferred embodiment will be described below.

FIG. 9 is a perspective view illustrating an electromagnet differentfrom the electromagnet 1 according to the first preferred embodiment.

In this example, the electromagnet 1A is formed preferably by stackingbase material layers 11 to 16. Terminal electrodes 11A and 11B, in-planecoil conductors 12A, 13A, and 14A, and dummy patterns 21 to 23 areprovided on one main surfaces of the base material layers 11 to 14. Basematerial layers 15 and 16 are further stacked on the base material layer14. An in-plane coil conductor is not provided on any of the mainsurfaces of the base material layers 15 and 16.

Specifically, in this example, the coil conductor including the in-planecoil conductors 12A, 13A, and 14A are located close to the side of thebase material layer 11 among the base material layers 11 to 16. Thisconfiguration allows the coil conductor to be close to the permanentmagnet 100, thus increasing an influence of the electromagnet to thepermanent magnet 100. Accordingly, the responsiveness of the permanentmagnet 100 to the displacement in the X direction is enhanced.

Second Preferred Embodiment

An electromagnet according to a second preferred embodiment of thepresent invention will be described below. The second preferredembodiment is different from the first preferred embodiment in thatdummy patterns are provided only for the displacement direction of thepermanent magnet disposed just above the electromagnet.

FIG. 10 is an exploded perspective view of an electromagnet according tothe second preferred embodiment.

Similar to the first preferred embodiment, the electromagnet 2 includesa stacked body 40 formed preferably by integrally stacking insulatingbase material layers 41, 42, 43, and 44. The base material layers 41 to44 are one example of an insulating substrate according to a preferredembodiment of the present invention. The base material layers 41 to 44are made of thermoplastic resin having flexibility, such as LCP resin.The stacked body 40 is formed preferably by heat-sealing the basematerial layers 41 to 44 to one another by hot pressing.

Terminal electrodes 41A and 41B are provided on one main surface (one ofa front surface and a back surface) of the base material layer 41.

Each of in-plane coil conductors 42A, 43A, and 44A is provided on onemain surface (one of a front surface and a back surface) of each of thebase material layers 42 to 44. An interlayer connection conductorindicated by a broken line in the figure is provided on each of the basematerial layers 42 to 44. The in-plane coil conductors 42A, 43A, and 44Aare connected to one another with the interlayer connection conductors,such that a coil 45 over a plurality of layers is provided. Morespecifically, one ends of the in-plane coil conductors 42A and 43A areconnected to each other. One ends of the in-plane coil conductors 43Aand 44A are also connected to each other.

As described above, the coil 45 includes the in-plane coil conductors42A to 44A, and the interlayer connection conductors. One end of thein-plane coil conductor 42A, which is a first end of the coil 45, isconnected to the terminal electrode 41A with the interlayer connectionconductor provided on the base material layer 41. One end of thein-plane coil conductor 44A, which is a second end of the coil 45, isconnected to the terminal electrode 41B with the interlayer connectionconductors provided on the base material layers 41 to 43.

Dummy patterns 51A, 51B, 52A, 52B, 53A, and 53B are respectivelyprovided on the base material layers 42 to 44. The dummy patterns 51A to53B are provided on the same main surfaces of the respective basematerial layers 42 to 44 as the main surfaces on which the in-plane coilconductors 42A, 43A, and 44A are located.

The dummy patterns 51A and 51B extend along an edge of the base materiallayer 42 in the X direction so as to sandwich the in-plane coilconductor 42A. The dummy patterns 52A and 52B extend along an edge ofthe base material layer 43 in the X direction so as to sandwich thein-plane coil conductor 43A. The dummy patterns 53A and 53B extend alongan edge of the base material layer 44 in the X direction so as tosandwich the in-plane coil conductor 44A. The dummy patterns 51A to 53Bare electrically isolated from other elements including the coil 45.

A permanent magnet 100 displaceable in the X direction is disposed justabove the electromagnet 2 thus configured. This permanent magnet 100 isdisplaced in the X direction by a magnetic field (electromagnetic force)from the electromagnet 2. The dummy patterns 51A to 53B define andfunction as a magnetic field shield for the magnetic field generatedfrom the coil 45 upon a change in a current flowing through the coil 45,as in the first preferred embodiment. Thus, the dummy patterns 51A to53B define and function as a magnetic field shield to increase theintensity of the magnetic field in the Z direction.

In this example, the dummy patterns 51A to 53B extend along the Xdirection, and they are not provided in the Y direction in which thepermanent magnet 100 is not displaced. With this, the dummy patterns areable to be smaller than in the first preferred embodiment. Accordingly,the formation space of the dummy pattern is reduced, such that the sizesof the base material layers 41 to 44 are able to be decreased more.

Notably, the dummy patterns 51A to 53A and the dummy patterns 51B to 53Bmay be provided on overlapped positions in the Z direction, and as inthe first preferred embodiment, the dummy patterns 51A to 53A may beconnected with interlayer connection conductors located on the basematerial layers 42 and 43, and the dummy patterns 51B to 53B may beconnected with interlayer connection conductors located on the basematerial layers 42 and 43.

A stress distribution portion may be provided on each of the in-planecoil conductors 42A, 43A, and 44A, each of the dummy patterns 51A to53A, and each of the dummy patterns 51B to 53B for stress distributionof the base material layers 41 to 44. FIG. 11 is a view illustrating oneexample of an in-plane coil conductor and a dummy pattern including astress distribution portion formed thereon. FIG. 11 illustrates the basematerial layer 42 in FIG. 10 as one example.

For example, the in-plane coil conductor 42A and the dummy pattern 51Bpreferably have a winding shape including a plurality of linearportions. Bent portions 42B and 51C which are bent may be provided onthe linear portions thereof. The bent portion 42B of the in-plane coilconductor 42A is bent to project in the direction away from theadjacently disposed dummy pattern 51B. The bent portion 51C of the dummypattern 51B is bent to project in the direction away from the adjacentlydisposed in-plane coil conductor 42A. The bent portions 42B and 51C maybe bent to project in the direction close to the dummy pattern 51B andin the direction close to the in-plane coil conductor 42A, respectively.The in-plane coil conductor 42A and the dummy pattern 51B may includewide portions 42C and 51D, which are wider than the other portions inthe direction perpendicular or substantially perpendicular to thedirection in which the linear portions extend. The stress distributionportion may be provided on plural positions of the in-plane coilconductor and the dummy pattern, or on only one position.

The formation of the stress distribution portion distributes stressinvolved with a flow of resin upon a heat and pressure treatment withthe base material layers 41 to 44 being stacked. This prevents thepossibility in which, during the production process, the in-plane coilconductor and the dummy pattern tilt in the stacking direction with theflow of resin to be in contact with each other (short-circuited), andhence, the performance of the coil 45 cannot be obtained. This alsoprevents the possibility in which the in-plane coil conductor and thedummy pattern are twisted due to the twist of the base material layers41 to 44 such that the in-plane coil conductor and the dummy pattern areshort-circuited (in contact with each other) or damaged. A non-linearportion such as a corner (curved portion) of the in-plane coil conductor42A is more difficult to tilt than the linear portion. Therefore, it iseffective to form the stress distribution portion on the linear portion.

The stress distribution portion may be applied to the electromagnet 1according to the first preferred embodiment.

Third Preferred Embodiment

FIG. 12 is a front sectional view of an electromagnet according to athird preferred embodiment of the present invention. In this preferredembodiment, an electromagnet 3 includes a stacked body 70. This stackedbody 70 is formed preferably by integrally stacking a plurality ofinsulating base material layers. The base material layer is made offlexible thermoplastic resin such as LCP resin. The stacked body 70 isformed preferably by hot pressing the base material layers.

The stacked body 70 includes a first main surface 70A and a second mainsurface 70B on the same side of the edge in the Z direction, the firstmain surface 70A and the second main surface 70B having differentheights in the Z direction. In other words, the stacked body 70 includesa step. A coil 60 is located at the side of the first main surface 70A.Similar to the first and second preferred embodiments, the coil 60includes an in-plane coil conductor located on one main surface of eachof the base material layers in the stacked body 70, in which thein-plane coil conductors are connected to one another with interlayerconnection conductors.

A terminal 80A that mounts an external element 80 is provided on thesecond main surface 70B of the stacked body 70. The coil 60 is connectedto the external element 80 at its one end via a connection conductor60A.

Dummy patterns 61A and 61B are located outside of the coil 60. The dummypattern 61B is provided at the step of the stacked body 70 and close tothe side of the second main surface 70B. If the dummy pattern 61B is notprovided, a boundary between the first main surface 70A and the secondmain surface 70B is made of only resin. Therefore, the stacked body maybe damaged upon the integral formation. In view of this, the dummypattern 61B is located inside, and this stabilizes the shape of thestep, as well as increases the intensity of the electric field of theelectromagnet 3.

Even when the first main surface 70A becomes a mounting surface on whichother elements are mounted, the first main surface 70A is able to bemade flat by stabilizing the shape of the step. This prevents problemsin which other elements cannot be mounted or other elements are mountedas being floated from the first main surface 70A.

Fourth Preferred Embodiment

FIG. 13 is a perspective view of an electromagnet 4 according to afourth preferred embodiment of the present invention. FIG. 14 is anexploded view of the electromagnet 4 according to the fourth preferredembodiment.

The electromagnet 4 includes a stacked body 71. The stacked body 71 isformed preferably by integrally stacking insulating base material layers71A, 71B, 71C, and 71D. Each of the base material layers 71A, 71B, 71C,and 71D is made of thermoplastic resin having flexibility, such as LCPresin (liquid crystal polymer resin). The stacked body 70 is formedpreferably by heat-sealing the base material layers 71A, 71B, 71C, and71D to one another by hot pressing. FIG. 14 illustrates only four basematerial layers. However, the number of the stacked layers in thestacked body 71 is not limited thereto.

Four coils 72, 73, 74, and 75 are provided on the stacked body 70. Thecoils 72, 73, 74, and 75 are arranged such that in-plane coil conductors72A, 73A, 74A, and 75A provided on the main surface of the base materiallayer 71A, in-plane coil conductors 72B, 73B, 74B, and 75B provided onthe main surface of the base material layer 71B, in-plane coilconductors 72C, 73C, 74C, and 75C provided on the main surface of thebase material layer 71C, and in-plane coil conductors 72D, 73D, 74D, and75D provided on the main surface of the base material layer 71D areconnected to one another with unillustrated interlayer connectionconductors.

The in-plane coil conductors 72A, 73A, 74A, and 75A are provided on coilformation regions A11, A12, A13, and A14 of the base material layer 71A.The in-plane coil conductors 72B, 73B, 74B, and 75B are provided on coilformation regions A21, A22, A23, and A24 of the base material layer 71B.The in-plane coil conductors 72C, 73C, 74C, and 75C are provided on coilformation regions A31, A32, A33, and A34 of the base material layer 71C.The in-plane coil conductors 72D, 73D, 74D, and 75D are provided on coilformation regions A41, A42, A43, and A44 of the base material layer 71D.

Dummy patterns 76A, 76B, 76C, and 76D are provided on the region otherthan the coil formation region on the main surface of each of the basematerial layers 71A, 71B, 71C, and 71D. The dummy patterns 76A, 76B,76C, and 76D are connected to one another with unillustrated interlayerconnection conductors. These dummy patterns 76A, 76B, 76C, and 76D areelectrically isolated from other elements including coils 72 to 75. Asdescribed in the first preferred embodiment, the dummy patterns 76A,76B, 76C, and 76D define and function as a magnetic field shield for amagnetic field generated from the coils 72 to 75 upon a change in acurrent flowing through the coils 72 to 75, such that the intensity ofthe magnetic field is increased.

The stacked body 71 includes an opening 77A that penetrates in thestacking direction. The opening 77A is surrounded by four coils 72 to 75in a plan view. A later-described camera lens is inserted into thisopening 77A. The stacked body 71 also includes a cutaway section 77Bextending from the opening 77A to the outer edge. The cutaway section77B is located on a region where four coils 72 to 75 are not provided.

The base material layers 71A, 71B, 71C, and 71D are made ofthermoplastic resin. With this configuration, when the base materiallayers 71A, 71B, 71C, and 71D are stacked, and formed integralpreferably by hot pressing, the stacked body 71 generates internalstress due to a difference in thermal expansion coefficient between boththe coils 72 to 75 and the dummy patterns and the base material layers71A, 71B, 71C, and 71D. When the pressing pressure is released, thestacked body 71 warps due to the internal stress. In view of this, thecutaway section 77B is provided on the stacked body 71. The cutawaysection 77B releases the internal stress to prevent the warpage of thestacked body 71.

The cutaway section 77B is able to be located at any position where thecoils 72 to 75 are not formed. For example, in FIGS. 13 and 14, thecutaway section 77B is preferably located between the opening 77A andthe outer edge of the long side of the stacked body 71. However, thecutaway section 77B may be located between the opening 77A and the outeredge of the short side of the stacked body 71. In this case, the lengthof the cutaway section becomes large, which releases more internalstress generated upon hot pressing.

The number of the coils in the electromagnet 4 is not limited to four.It is only necessary that a plurality of coils are provided. Theposition where the coils 72 to 75 are located is not particularlylimited, so long as they are located at a position surrounding theopening 77A.

A non-limiting example of a production method of the electromagnet 4will be described below.

Firstly, a copper foil is attached to one surface of a base materialsheet made of thermoplastic resin. Alternatively, a sheet with copperattached to one surface is prepared. A resist film is patterned on thecopper foil according to the in-plane coil conductors and the dummypatterns to be formed. An etching is performed to form each pattern, andthen, the resist film is removed. Thereafter, each position where theinterlayer connection conductor is to be formed is irradiated with laserlight from the other surface (on which the copper foil is not attached)of each of the base material sheets to form a hole. A conductive pastecontaining Su, Cu, Ni, Ag, etc. is filled in this hole.

The formed base material sheets are stacked. In this case, each of thebase material sheets is stacked on the main surface on which eachpattern is formed. A heat and pressure treatment (hot press) is appliedto the stacked base material sheets to bond these sheets. The basematerial sheets are thermoplastic resin as described above, so that anadhesive agent does not need to be used. Further, damage (crack) uponcuring is prevented. The opening 77A and the cutaway section 77B areformed after the hot pressing of the stacked base material sheets. Thus,the electromagnet 4 is produced. With the opening 77A and the cutawaysection 77B provided after the hot pressing of the stacked base materialsheets, a loss of the shape due to a resin flow upon the hot press isprevented, and further, short-circuiting of the conductors hardlyoccurs.

The opening 77A and the cutaway section 77B are not necessarily formedafter the hot pressing of the stacked base material sheets.Specifically, after the opening and the cutaway section are formed oneach of the base material sheets, the base material sheets may bestacked, and hot pressing may be performed on the stacked base materialsheets.

As in the first preferred embodiment, the electromagnet is able to beused as a so-called voice coil motor, when permanent magnets aredisposed just above the coils 72 to 75. A camera module including thevoice coil motor for a camera shake correction will be described below.

FIG. 15 illustrates a plan view of a camera module 210 provided with theelectromagnet 4 according to the present preferred embodiment, and asectional view taken along a line XV-XV. This camera module 210 is oneexample of a “camera lens driving device”.

The camera module 210 includes the electromagnet 4 and a frame 211. Theelectromagnet 4 is provided below the frame 211 with a gap (e.g., about500 μm or less) between the frame 211 and the electromagnet 4. Theelectromagnet 4 and the frame 211 are connected with a wire 215. Theframe 211 is displaceable, and the displacement is restricted by thewire 215.

As described with reference to FIG. 13, the electromagnet 4 includes theopening 77A. The frame 211 includes a hole, not illustrated, located atthe center of a flat plate, and this hole is overlapped with the opening77A of the electromagnet 4. A lens holder 212 is inserted into the holeon the frame 211 and the opening 77A of the electromagnet 4, and isfixed at the hole of the frame 211. The lens holder 212 holds a cameralens 213. Specifically, the camera lens 213 is displaced together withthe lens holder 212 and the frame 211 within a range inside of theopening 77A of the electromagnet 4.

Permanent magnets 100A, 100B, 100C, and 100D are provided on the flatplate of the frame 211 so as to surround the lens holder 212 on all foursides. These permanent magnets 100A, 100B, 100C, and 100D are disposedjust above the coils 72 to 75 in the electromagnet 4.

The displacement of the camera lens 213 and other components is similarto FIGS. 8A and 8B, so that the description thereof will not berepeated.

As described above, in the present preferred embodiment, the coils 72 to75 defining and functioning as an actuator are preferably integral, suchthat misalignment upon the arrangement is more significantly reduced orprevented than the case where the coils 72 to 75 are independentlyformed and used for the camera module 210. The electromagnet preventswarpage caused upon hot pressing to prevent displacement in thedirection in which the electromagnetic force is generated. This enablesprecise displacement of the camera lens 213 in the camera module 210,thus achieving precise camera shake correction.

While preferred embodiments of the present invention have been describedabove, it is to be understood that variations and modifications will beapparent to those skilled in the art without departing from the scopeand spirit of the present invention. The scope of the present invention,therefore, is to be determined solely by the following claims.

What is claimed is:
 1. A stacked body comprising: a base including aplurality of the insulating base material layers; a coil including awinding-shaped conductive pattern located on at least one of theplurality of the insulating base material layers; and an electricallyisolated dummy pattern extending along at least a portion of the coiloutside of the coil on at least one of the plurality of the insulatingbase material layers in a plan view; wherein the stacked body includes astep at which a thickness of the stacked body is different in a stackingdirection in which the plurality of insulating base material layers arestacked; and the dummy pattern is located between the coil and the stepat a portion defining the step where the thickness of the stacked bodyis larger.
 2. The stacked body according to claim 1, wherein the dummypattern is located on the same insulating base material layer as the atleast one of the insulating base material layers on which the conductivepattern is located.
 3. The stacked body according to claim 1, whereinthe dummy pattern is located on the plurality of insulating basematerial layers.
 4. The stacked body according to claim 3, wherein thedummy pattern is located on all of the insulating base material layerson which the conductive pattern is located.
 5. The stacked bodyaccording to claim 1, wherein a conductor connected to the dummy patternand extending in the stacking direction is located on an insulating basematerial layer located above or below the dummy pattern in the stackingdirection.
 6. The stacked body according to claim 5, wherein: the dummypattern is located on the plurality of insulating base material layers;and the conductor extending in the stacking direction connects the dummypatterns located on different insulating base material layers to eachother.
 7. The stacked body according to claim 1, wherein the dummypattern sandwiches at least the conductive pattern in a plan view. 8.The stacked body according to claim 7, wherein the dummy patternencloses the conductive pattern in the plan view.
 9. The stacked bodyaccording to claim 8, wherein the dummy pattern is annular and enclosesthe conductive pattern in the plan view.
 10. The stacked body accordingto claim 1, wherein each of the plurality of insulating base materiallayers is a flexible resin base material layer.
 11. The stacked bodyaccording to claim 10, further comprising: an opening penetrating in thestacking direction; and a cutaway section extending from the opening toan outer edge; wherein a plurality of the conductive patterns areprovided around the opening; and the cutaway section is provided at aposition at which the plurality of conductive patterns are not provided.12. A method of producing a stacked body in which a plurality ofinsulating base material layers made of thermoplastic resin are stacked,the method comprising steps of: stacking the plurality of insulatingbase material layers made of thermoplastic resin; forming a coil and adummy pattern on at least one of the plurality of insulating basematerial layers; wherein: the coil includes a winding-shaped conductivepattern located on at least one of the plurality of the insulating basematerial layers; the dummy pattern is disposed outside of the coil as apattern isolated from the conductive pattern of the coil; the dummypattern extends along the coil; the stacked body includes a step atwhich a thickness of the stacked body is different in a stackingdirection in which the plurality of insulating base material layers arestacked; and the dummy pattern is located between the coil and the stepat a portion defining the step where the thickness of the stacked bodyis larger; and integrating the stacked plurality of insulating basematerial layers by applying heat and pressure.
 13. The method ofproducing a stacked body according to claim 12, further comprisingforming: an opening penetrating in the stacking direction; and a cutawaysection extending from the opening to outside in the plurality ofinsulating base material layers.
 14. The method of producing a stackedbody according to claim 13, wherein the step of forming the cutawaysection includes a step of forming the opening and the cutaway sectionafter the plurality of insulating base material layers are integrated inthe step of integrating.